Method for bleaching textiles

ABSTRACT

BLEACHING OF TEXTILE MATERIALS BY VAPOR PHASE TREATING THE FABRIC WITH AN ORGANIC HYDROPEROXIDE AS THE BLEACHING AGENT.

United States Patent Office 3,574,519 Patented Apr. 13, 1971 Int. Cl. D061 3/02 US. Cl. 8-111 7 Claims ABSTRACT OF THE DISCLOSURE Bleaching of textile materials by vapor phase treating the fabric with an organic hydroperoxide as the bleaching agent.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a method for bleaching textiles such as cotton fabrics to improve their brightness by bleaching the fabric with an organic hydroperoxide such as tertiary butyl hydroperoxide, the bleaching being carried out in the vapor phase.

Prior art The bleaching of textile materials, in particular cotton containing fabrics, has been carried out utilizing a wide variety of bleaching materials. In recent years hydrogen peroxide has become an important bleaching agent for such materials. It has been estimated that hydrogen peroxide is used to bleach approximately 85 percent of all the cotton bleached in the United States annually. Hydrogen peroxide despite its high cost and instability has become this widely used because it effectively bleaches with few undesirable side reactions or after effects.

In addition to bleaching pure cotton, hydrogen peroxide is becoming increasingly important for bleaching blends of cotton and synthetic fibers.

Cotton bleaching with hydrogen peroxide consists of several steps. The fabric is dipped in a bleach solution which consists of hydrogen peroxide and a buffer such as sodium silicate together with sodium hydroxide. The excess solution is squeezed from the cloth by passing it between rollers so that an amount of solution approximately equal to the weight of the cloth is left in the cloth. The cloth is then passed into a J-box where it is heated in a counter-current flow of steam at 210 F. for about one hour. The cloth is then stored to allow the bleaching reactions to be completed and finally the cloth is washed to remove bleaching solution and bleaching by-products.

Recently, olefin epoxidation processes have been developed which use organic hydroperoxides, in particular tertiary butyl hydroperoxide, as the oxidizing agent with the reaction being catalyzed by a molybdenum-containing catalyst. This development has created a large demand for hydroperoxides which has led in turn to the development of commercial methods for producing hydroperoxides at an economical price.

It now have been found in accordance with the method of this invention that these hydroperoxides which can be produced economically can also be used as the bleaching agent for cotton fabrics instead of the more costly hydrogen peroxide, thereby providing marked savings in bleaching costs. In addition, hydroperoxides have other advantages over hydrogen peroxide as will be described.

SUMMARY OF THE INVENTION In accordance with this invention an organic hydroperoxide such as tertiary butyl hydroperoxide is utilized in the vapor phase to bleach cotton materials, in particular cotton fabrics. In a specific embodiment of the invention the bleaching step is accompanied by the use of a mild buffering agent such as sodium tripolyphosphate.

In a further specific embodiment of the invention the hydroperoxide bleaching step is followed by an aftertreatment step with a sulfite compound such as sodium sulfite, sodium hydrosulfite, zinc hydrosulfite or the like.

It is an object of this invention to provide a novel method for bleaching cotton materials.

It is another object of this invention to provide a method for bleaching cotton materials utilizing an organic hydroperoxide as the bleaching agent.

It is another object of this invention to provide a method for bleaching cotton materials utilizing an organic hydroperoxide in combination with a mild buffering agent.

It is another object of this invention to provide a method for bleaching cotton materials utilizing an organic hydroperoxide followed by treatment with a sulfite compound.

Other objects of this invention will be apparent from the following description of the preferred embodiments and from the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of this invention is particularly adapted for bleaching cotton fibers and materials, in particular cotton fabrics including mixtures of cotton with other fibers including synthetic fibers such as Dacron and the like.

Since by the method of this invention, organic hydroperoxides, in particular tertiary butyl hydroperoxide, can be used in the same amounts as hydrogen peroxide to give equally good bleaching of cotton materials and since the hydroperoxides can be produced at a considerably lower cost than the hydrogen peroxide there is a distinct advantage for utilizing the hydrop eroxides.

In addition to the economic advantage for the hydroperoxides they have the additional advantage of having greater stability as compared with hydrogen peroxide. Hydrogen peroxide unless special precautions are followed, decomposes even at ordinary temperatures to give water and oxygen. This type of oxygen evolved does not result in bleaching. Special precautions are not necessary with organic hydroperoxides since they decompose only at elevated temperatures. For example, tertiary butyl hydroperoxide starts to decompose only at about C.

Other organic hydroperoxides in addition to tertiary butyl hydroperoxide are also available commercially, for example, cumene hydroperoxide and the amyl hydroperoxides. These hydroperoxides can be utilized to the same advantage as the tertiary butyl hydroperoxide.

Bleaching by the method of the instant invention provides important advantages over the hydrogen peroxide process. The hydroperoxides require no special handling to avoid spontaneous oxygen release. Solutions of hydrogen peroxide must be prepared daily, since oxygen continuously evolves from bleach solutions containing hydrogen peroxide. Hydroperoxide bleach solutions maintain a constant active oxygen content for many weeks or months.

In the instant invention the fabric is first preferably wetted with a buffer or alkaline solution, for example, the fabric may be sprayed with a sodium or potassium tripolyphosphate solution until an amount of solution about equal in weight to the weight of the fabric is adsorbed by the fabric. The fabric is then introduced into an atmosphere of water vapor and tertiary butyl hydroperoxide vapor in equilibrium with the liquid phase. The fabric is held in this Vapor which is in equilibrium with the liquid phase held at a temperature of about 70 C. for from about 1 to 4 hours.

In one embodiment the vapors are allowed to condense on the walls of the container and atmospheric pressure is utilized. In another embodiment the fabric is held in the vapor container which is completely closed so that the pressure attained in the vapor phase is dependent on the temperature to which the liquid is heated, i.e. it will be at super-atmospheric pressure. Under the latter conditions the bleaching will occur more rapidly.

It is generally preferable to follow the bleaching step with an after-treatment with a sulfite compound to avoid color reversion due to active oxygen containing compounds remaining in the fabric and to complete the decolon'zation process.

In order to determine the effectiveness of tertiary butyl hydroperoxide as a bleaching agent for cotton fabrics a piece of unbleached cottom 100 yards long by 12 inches wide was obtained from a manufacture of such standard cloth well recognized in the industry. There was also obtained a sample of the same fabric which had been bleached to a brightness acceptable to the fabric industry. The reflectance of the fabric was measured by a Photovolt Reflection Meter Model 610, manufactured by the Photovolt Corp. and provided with a search unit 610Y with a Green-Tristirnulus Filter. The meter was adjusted so that a standard magnesium oxide block read 100 and the unbleached fabric read 65. At this setting the bleached standard read 72. In all of the tests which are set forth in the examples herein this fabric was employed and the described Photovolt reflectance meter settings were used.

In the bleaching tests, swatches measuring 2" x 4 were cut from the large piece. They weighed 0.54 gram plus or minus 0.01 gram.

The hydrogen peroxide bleach solutions used for comparative tests were made fresh daily by dilution of commercial percent hydrogen peroxide with water to 1 percent (grams/ml.). The peroxide content was checked by titration, with standard thiosulfate, of the iodine liberated from potassium iodide.

The tertiary butyl hydroperoxide solutions were made from commercial tertiary butyl hydroperoxide of approximately 90 pecent strength. They were diluted with water to 1 percent concentration. The concentration was checked by thiosulfate titration.

The sodium silicate used as a buifer was added to the bleach solution as a -42 B. solution assuming it to be 100 percent sodium silicate. Sodium hydroxide was added as anhydrous pellets.

EXAMPLE I Runs were made at the liquid phase to compare tertiary butyl hydroperoxide with hydrogen peroxide as a bleaching agent for cotton fabric. The conditions described for the commercial hydrogen peroxide process were approximated on a laboratory scale. The cotton fabric swatches were rolled about their short axis and placed in 2" high by 1 /2" inside diameter glass bottles. A 0.5 gram sample of bleach solution was added to the bottle and the solution allowed to wick through the swatch. Following application of the bleach solution the uncapped bottles containing 1 swatch each were heated at 100 C. for one hour in an oven during which time the water and bleach evaporated. The photometer brightnesses were then read.

In Table I are set forth the bleach solutions, buffer solutions, after-treatment and reflectance measurements for a series of comparative runs. In each of these runs the percent of hydrogen peroxide, tertiary butyl hydroperoxide, buffer and bisulfite are weight percent based on the weight of the dry fabric.

TABLE I Photometer Bleach Buffer After treat reading No N0 N 65 ysyfifioz ,7sil i1c at ta gun" 2 a 202" 2 51108. e o 4% H 02" do 2% NaHSOa 71 1% H201. 1% silicate No 70 H202. d0 2% NaHSOa 72 2% H 0 2% silicate N0 70 2% H O d0 1.. 2% NaHSO 65 68 65 68 65 68 66 4% TBHP Same 2% NaHSOa 68 IIP=tertiary butyl hydroperoxide.

STPP =sodium tripolyphosphate.

It will be noted that under these conditions the hydrogen peroxide increases brightness from 65 to 72, whereas the tertiary butyl hydroperoxide increases it only from 65 to 68. It will also be noted that varying the conditions would not increase the tertiary butyl hydroperoxide brightness readings. In addition to these runs, runs with sodium silicate instead of sodium tripolyphosphate gave a 1 point lower reading over the range of bleach concentrations. Also, heating at 110 C. for one hour gave no change in the tertiary butyl hydroperoxide readings. It will be seen, therefore that tertiary butyl hydroperoxide gives less than the desired optimum bleaching at these conditions.

EXAMPLE 11 In order to demonstrate the effectiveness of tertiary butyl hydroperoxide as a bleaching agent in the vapor phase, runs were carried out wherein the cotton fabric was exposed to the vapor and condensing vapors above water solutions of tertiary butyl hydroperoxide. The 2" x 4" swatches rolled about the 2" axis were hung by thin wires in 3" high by 2" inside diameter jars. The swatches were hung in the vapor space above 5 to 10 mls. of aqueous bleach solution. The jars were heated to a bleaching solution temperature of 70 C. on a heated plate and the vapors from the solution condensed on the fabric and on the vessel walls.

After exposure to the bleaching 'vapors for various time periods the swatches were placed in dry glass jars at C. for one hour to dry. Brightnesses were read and the results are set forth in Table II.

In these runs neither pre-treatment nor after-treatment was employed.

TAB LE II NOTE.TBHP=tertiary butyl hydroperoxide.

These results show that vapor phase bleaching gives an improvement over a liquid phase bleaching.

EXAMPLE HI In order to demonstrate that vapor phase bleaching with pie-treatment and after-treatment gives effective results with tertiary butyl hydroperoxide as the bleaching agent a number of runs were carried out utilizing these three stages. The 2" by 4" cotton swatches were sprayed with the buffer solutions prior to inserting them into the bleaching vapor. The solution was sprayed on the swatches by the use of an atomizer and it was found that the swatches absorbed an amount of buffer solution twice their own weight within plus or minus percent. The spray so utions were made up to 1 percent as has been described so that the pre-treating gives 2 percent of the buffer based on the weight of the cloth. Some runs were 6 these commercial sodium silicate 40-42 B. or possibly sodium carbonate on a cost basis would be practical.

EXAMPLE IV In order to make a direct comparison with hydrogen peroxide bleaching, identical runs were carried out in the manner of Example III under the conditions shown in Table IV comparing hydrogen peroxide with tertiary butyl hydroperoxide.

NOTE.TBHP tertiary butyl hydroperoxide.

made with only 1 percent buffer based on weight of the cloth but no appreciable difference was noted. The bleaching was carried out in the same manner as described in Example 11 except that in some instances cylinders 6 inches in diameter and 7 inches high with glass covers were employed. The cylinders allowed hanging of 10 to swatches from a Wire spanning the cylinders diameter. The cylinder required ml. of bleach so ution to cover the bottom with liquid. No appreciable difference in bleaching results was found with the change in vessels.

The temperature of the bleach solution was kept at C. by standing the vessels on a hot plate. Some liquid condensed and ran down the vessel walls but there was no liquid dropping from the swatches. The sodium bisulfite aftertreatment was on a 2 percent on weight of cloth basis applied as a 1 percent solution. The after-treatment was applied as described in Example I. The results obtained in these various runs are shown in Table III.

These runs show that the vapor phase bleaching with tertiary butyl hydroperoxide gives equally good results as with hydrogen peroxide.

As many possible embodiments can be made of this invention without departing from the broad scope thereof, it is to be understood that all matter herein set forth is to be interpreted as illustrative and not as unduly limiting the invention.

We claim:

1. A method of bleaching cotton textile materials which comprises contacting said material with an organic hydroperoxide selected from the group consisting of tertiary butyl hydroperoxide, cumene hydroperoxide and amyl hydroperoxide in the vapor phase at a temperature of about 70 C. and atmospheric pressure for from 1 to 4 hours.

2. The method according to claim 1 wherein the organic hydroperoxide is tertiary butyl hydroperoxide.

TABLE III Photom- Photometer eter Pretreat Bleach Hours reading After treat reading STPP 271, TBHP...

.do. 5% TBHP NaHSO; .do Same SRPP 5% trAmyl- .-.do

hdydroperox- 1 e.

Zn dithionate.

1 Each salt at 1% concentration based on weight of cloth. 2 Bleach at 80 0. NOTE:

SIPP =sodium tripolyphosphate.

TBHP=tertiary butyl hydroperoxide.

It will be seen that increasing the temperature from 70to 80 0. gave no change in bleaching results. There was no detectable difference between 5 percent and 12 percent tertiary butyl hydroperoxide bleach solutions. A 1 percent solution (not included in the Table III), however, gave lower photometer readings. It will be seen that 3. The method according to claim 1 wherein the or- 4. The method according to claim 1 wherein the organic hydroperoxide is amyl hydroperoxide.

5. The method according to claim 1 wherein the fabric is pretreated with a butler or alkaline aqueous solution a wide range of pretreat salts are practical and among prior to contacting with the organic hydroperoxide, said buffer or alkaline solution being an alkali metal compound selected from the group consisting of sodium tripolyphosphate, potassium tripolyphosphate, sodium silicate, sodium bisulfite, and sodium hydroxide.

6. The method according to claim 1 wherein the organic hydroperoxide treating step is followed by treatment with sodium bisulfite.

7. The method according to claim 1 wherein the fabric is treated with a buflFer or alkaline aqueous solution prior to contacting with the organic hydroperoxide and there- 10 after the fabric is treated with sodium bisulfite, said buffer or alkaline solution being an alkali metal compound selected from the group consisting of sodium tripolyphosphate, potassium tripolyphosphate, sodium silicate, sodium bisulfite, and sodium hydroxide.

References Cited UNITED STATES PATENTS 6/1957 Emerson et a1 8111X 1 1/1958 Hawkinson et a1 8-1 11X US. Cl. X.R. 

